1. Field of the Invention
The present invention relates to a battery unit for lens-fitted photo film unit. More particularly, the present invention relates to a battery unit for lens-fitted photo film unit in which a battery is contained for powering a flash device, and can be enclosed in a reliably watertight manner even by a simple structure.
2. Description Related to the Prior Art
A lens-fitted photo film unit as a single-use camera pre-loaded with photo film. After a user takes photographs by use of the lens-fitted photo film unit, he or she does not remove photo film, but can forward the lens-fitted photo film unit simply to a photofinisher to ask for printing photographs. Because of good availability and great ease in handling, the lens-fitted photo film unit is widely used today.
There is a flash built-in type of the lens-fitted photo film unit useful in taking photographs at night, indoors, with a rear light and the like. In general, the lens-fitted photo film unit includes a main body and an exposure unit in front of the main body. For emission of flash light, a flash device has a circuit board, which is disposed in a space between the exposure unit and a roll holder chamber formed in the main body. A battery is used as power source for the flash device. An example of the battery is an alkali battery of the AA type. The battery is oriented to lie horizontally in the longitudinal direction of the main body. At least one battery electrode of the battery is located farther from the circuit board. A contact segment of the circuit board for contact with the battery electrode is constituted by an arm portion, which has a considerable length near to that of the battery, for example approximately 40 mm. The battery is held with the circuit board by squeezing of the contact segment.
For a user to use the lens-fitted photo film unit in an underwater scene, there is a waterproof type of the lens-fitted photo film unit available commercially. A waterproof case is used to accommodate the lens-fitted photo film unit. The waterproof type also includes the flash device and the battery. In the known type, it is likely that the waterproof case is broken if the lens-fitted photo film unit is dropped and shocked considerably. Water may permeate the inner elements of the lens-fitted photo film unit. The battery is likely to corrode, to cause solution leakage of electrolyte. A similar problem may occur in the general-use type without waterproofness. If the lens-fitted photo film unit is used at the time of a rainfall outdoors, the solution leakage may occur in the battery because of entry of water. In considering that the battery is an alkali battery, the electrolyte of a strong alkali is harmful to human bodies, may cause alkali burn to a user's hands, or enter the user's eye.
To solve those problems, there have been various suggestions. JP-A 11-271933 discloses a flash built-in type of the lens-fitted photo film unit in which a battery chamber contain the battery and has a watertight structure. According to this document, the electrolyte does not flow out of the battery chamber even if the solution leakage of the electrolyte occurs from the battery. This is effective in preventing accidents such as burn of hands of a user because of the strong alkali.
The structure of JP-A 11-271933 has a problem in lack of consistency to recycling of parts. It is difficult to reduce a manufacturing cost. The above-mentioned structure with the arm portion for connection with the battery is suitable for recycling, but cannot be combined with the structure in the prior document. There is no structure having both the suitability for recycling and reliable watertightness.